Help Landing on Eve

[Aegolius13]

Hi guys,

I am trying to land an ascent vehicle (about 100 tons) on Eve and am having serious trouble getting it to the ground intact.  At first I tried putting an inflatable heat shield on the front, so I could continue to use my engines to tweak my orbit in between aerobraking passes.  This would also let the heat shield dislodge pretty cleanly.  But not surprisingly, the thing flipped since my center of mass is far in the back, making the rest of the rocket blow up.  

Next attempt: I tried putting two inflatable heat shields on the rear, attached to the back of two fuel pontoons.  These were barely enough to let me aerobrake safely, though I frequently had to reload since the a tiny bit of extra wobble led to blow-ups.  This method was also problematic since I could not use my shields, meaning I had no way to control the descent path and ended up landing in the sea.  (I might experiment with Vernors or other small engines pointing backwards for this bit).

But the bigger problem with putting heat shields on the back was getting the darn things off.  Even after my chutes deployed and my velocity was slowed down to about 15 m/s, they would not jettison without pushing upward and breaking up my rocket. Looks like their terminal velocity on Eve is close to nothing.  With smaller rockets, I've had some luck using my reaction wheels to flip my craft at least to the side, then dumping the shield.  But this does not seem to work on my bigger rocket, especially after the chutes deploy.

I'm considering trying separatrons or something similar to push the pontoons down and out when I jettison the heat shields, but I doubt they would have enough force to overcome the huge drag from the shields, especially in Eve's thick air.  

Any tips or tricks for how to get down safely?

 

Here's a pic of my lander core (I have slightly modified since then, but same general idea).  The heat shields on my second try were attached at the bottom of two orange tanks, which in turn were mounted to the side of this thing.  

 

[Magzimum]

I recently posted my Eve adventure on the Mission reports. I experienced the exact same problem, and went through 5 designs before finally getting it.

I went with the inflatable heat shield below the engines. That still flipped because I had a few stabilizer fins that were sticking out... so I put some large fins all the way at the top of the rocket, with airbrakes (pitch and yaw enabled!).

The heat shield also would not let go of my rocket, even with parachutes semi-deployed. But once the parachutes were fully deployed and I slowed down to 8-9 m/s, it finally separated. But I used only parachutes to slow me down (no engines)... I guess you're going with an engine-assisted landing, since I see only 6 parachutes? I don't know if those parachutes will slow you down enough to get rid of that heatshield.

My advice would be to increase the number of parachutes, and to put them on radial decouplers (e.g. TT-38K), so you can ditch them before launching off Eve's surface. (Also makes for good fireworks, since obvioulsly used parachutes will detonate when they hit Eve's surface at anything over 12 m/s).

 

[magnemoe]

Yes, inflatable heat shield in bottom, airbrakes works nice on top, if atatched to core stack they will be hidden from the heat by the inflatable heatshield but still produce drag. 
Plenty of reaction wheels also help, I put mine on the heat shield module who also held fuel and engines for deorbit burn. (using mechjeb and wanted to see trajectory with heatshield inflated and pointing retrograde). So I put an droge shute on that decent module. as soon as I was done with heating I turned off the airbrakes and rotated the lander bottom up, stage and open parashute on decent stage to get rid of it. 

It can be smart to use a bit fuel for the landing if the stage is heavy to slow you down just before hitting ground. 

[Aegolius13]

Thanks guys. I'll try throwing on a bunch more chutes on the descent nacelles, and putting a few airbrakes on with decouplers.  

[Aegolius13]

16 hours ago, magnemoe said:

Yes, inflatable heat shield in bottom, airbrakes works nice on top, if atatched to core stack they will be hidden from the heat by the inflatable heatshield but still produce drag. 
Plenty of reaction wheels also help, I put mine on the heat shield module who also held fuel and engines for deorbit burn. 

Good call.  I did a revised design with a couple large reaction wheels on the landing nacelles, and 6 airbrakes.  The ship held nice and steady through aerobraking and entry. 

 

21 hours ago, Magzimum said:

The heat shield also would not let go of my rocket, even with parachutes semi-deployed. But once the parachutes were fully deployed and I slowed down to 8-9 m/s, it finally separated. But I used only parachutes to slow me down (no engines)... I guess you're going with an engine-assisted landing, since I see only 6 parachutes? I don't know if those parachutes will slow you down enough to get rid of that heatshield.

I tried adding LOTS of chutes - I think 2 forward mounted XLs, and 24(!) of the radial ones.  This got my terminal velocity down to 7.2 m/s.  But still, the moment I detach the heat shields, they blow up my nacelles.  I don't know how much lower I can realistically get my terminal velocity, if it even matters.  When I turn on indestructibility and release the shields, they practically seem to float UP.  

Maybe I need to put some ballast on the heat shields so they'll fall better? ("Ballast" has to be a spaceship designer's least favorite word).  Currently I have the parachutes on my landing nacelles.  But perhaps I should move them back onto the ascent stage (on decouplers) so they'll stay up and the nacelles will fall.  My plan was to use the nacelles' last bit of fuel for engine assisted landing if necessary, plus lithobraking safety margin.  But if I coat my ascent module in parachutes, I might not need either.

Considering using the KAS explosives to blow up the darn things, but I consider that close to cheating.  

Argh, Eve is hard.  

Any other heat shield detachin' tricks would be greatly appreciated.

 

 

[gilflo]

You can look at my design in this topic

-inflatable shield below the engines to protect the whole ship. Must be ejectable with  parachutes opened on final

-Top device with a bunch of 8 speedbrakes to balance the ship during retrograde descent. Must be ejectable too, 

-depending if speedbrakes are efficient enough or not, you can set on COG a bunch of 4 to 8 vernors ( even more) WORKING WITH RCS to help balancing during descent. Must be coupled up to an ejectable tank, set with the speedbrakes device for example, and must be ejectable too.

-speedbrakes opened all time during descent, as long as overheeting is a factor, will be a great help to avoid flip. So wiil do the vernors with RCS, if speedbrakes are not enough during critical phases.

An important factor to avoid flipping during descent is a question of distance between COG and speedbrakes

 

[Aegolius13]

13 minutes ago, gilflo said:

inflatable shield below the engines to protect the whole ship. Must be ejectable with  parachutes opened on final

That's really the rub at this point.  I am good with not flipping (actually I don't think I could get the thing to flip, even if I tried), good with heat resistance, good slowing to safe chute speed, have enough chutes that it could land safely.  I just can't jettison the dang heat shields.  Do you recall what your velocity was when you did it, or if you used any other tricks?

EDIT: I just figured it out.  I had two heat shields overlapping slightly, in kind of an 8 or infinity shape.  Looks like this invited the Kraken.  If I cheat and release one shield, the other one drops off normally.  Now just need to redesign a one-shield lander...

Edited September 20, 2016 by Aegolius13

[Magzimum]

1 hour ago, Aegolius13 said:

I tried adding LOTS of chutes - I think 2 forward mounted XLs, and 24(!) of the radial ones.  This got my terminal velocity down to 7.2 m/s.  But still, the moment I detach the heat shields, they blow up my nacelles.  I don't know how much lower I can realistically get my terminal velocity, if it even matters.  When I turn on indestructibility and release the shields, they practically seem to float UP. 

From your description, I sense that the problem is not in the drag of the heat shields, but the explosives that are used to separate it. Try setting the ejection force to zero, so that they just decouple and are allowed to fall down. Then when your velocity is reduced to 7.2 m/s, they should separate without blowing anything up. The fact that stuff blows up at the moment you detach the heat shields suggests to me that we're not dealing with an impact of debris (at hasn't had the time to build up any velocity relative to your lander after all) but with something more buggy altogether.

As I said, my lander slowed down to only 8-9 m/s and I got rid of that heat shield. But I have had plenty of landers blow up when I separated that 10m heat shield, and they all blew up at the instant that I separated the heat shield. Those explosives that are used in the decoupler are a little suicidal, in my opinion.

1 hour ago, Aegolius13 said:

Argh, Eve is hard.  

It should be hard. We need a couple of good challenges in this game!

[edit] Ah, I read in your last post that you're identified the Kraken. Hopefully that solves the problem. Overlapping heat shields start acting like 2 separate parts of debris the moment you separate them. And since they overlap, all that teflon or ceramic material will obviously explode. Good luck!

Edited September 20, 2016 by Magzimum

[Aegolius13]

29 minutes ago, Magzimum said:

From your description, I sense that the problem is not in the drag of the heat shields, but the explosives that are used to separate it. Try setting the ejection force to zero, so that they just decouple and are allowed to fall down. Then when your velocity is reduced to 7.2 m/s, they should separate without blowing anything up. The fact that stuff blows up at the moment you detach the heat shields suggests to me that we're not dealing with an impact of debris (at hasn't had the time to build up any velocity relative to your lander after all) but with something more buggy altogether.

As I said, my lander slowed down to only 8-9 m/s and I got rid of that heat shield. But I have had plenty of landers blow up when I separated that 10m heat shield, and they all blew up at the instant that I separated the heat shield. Those explosives that are used in the decoupler are a little suicidal, in my opinion.

It should be hard. We need a couple of good challenges in this game!

[edit] Ah, I read in your last post that you're identified the Kraken. Hopefully that solves the problem. Overlapping heat shields start acting like 2 separate parts of debris the moment you separate them. And since they overlap, all that teflon or ceramic material will obviously explode. Good luck!

Just to confirm, I edited the save file to change the ejection force percent to zero (I think).  In any event, ship still blew up... just maybe a bit less energetically?  

At any rate I have a single heat-shield redesign that I'll try tomorrow.  Thanks for your help!

I do agree we need some difficult challenges.  After Eve I'll be done with most of the big ones... huh.  Guess it will be time to come back to Eve with a 20-kerbal tourist lander or something.  

[foamyesque]

Have you considered wings? They work great on Eve for aerobraking, landing, and even horizontal liftoff if you go that route (alternatively, you can jettison 'em and do your final landing on chutes, for a vertical takeoff).

It's a lot easier to test with HyperEdit, of course.

[gilflo]

7 hours ago, Aegolius13 said:

That's really the rub at this point.  I am good with not flipping (actually I don't think I could get the thing to flip, even if I tried), good with heat resistance, good slowing to safe chute speed, have enough chutes that it could land safely.  I just can't jettison the dang heat shields.  Do you recall what your velocity was when you did it, or if you used any other tricks?

EDIT: I just figured it out.  I had two heat shields overlapping slightly, in kind of an 8 or infinity shape.  Looks like this invited the Kraken.  If I cheat and release one shield, the other one drops off normally.  Now just need to redesign a one-shield lander...

Wait your chutes opened under 1000m and your speed is under 20m/s. Add some ullage engines to help separation

[Aegolius13]

3 hours ago, foamyesque said:

Have you considered wings? They work great on Eve for aerobraking, landing, and even horizontal liftoff if you go that route (alternatively, you can jettison 'em and do your final landing on chutes, for a vertical takeoff).

 

I've considered wings after loiking at some high efficiency designs on the forums, but since I'm (hopefully) close to a working design I think I'll save the wings for my next mission.

 

1 hour ago, gilflo said:

Wait your chutes opened under 1000m and your speed is under 20m/s. Add some ullage engines to help separation

I tried firing my main engines at the same time as dropping the shield, but that did not work either.  The problem really seems to be caused by the overlap between the two deployed heat shields. Plus, when I was only dropping the second one, it came off cleanly.

But if I still have problems detaching on the one shield design, I'll try some separatrons or something.

[genericeventhandler]

Slightly cheating  but. 

@PART[InflatableHeatShield]
{
	@MODULE[ModuleAnimateGeneric]
	{
		@disableAfterPlaying = false
	}
}

Add this as a .cfg anywhere in the gamedata folder, and deflate the shield before dumping it,   

GE

[Aegolius13]

12 minutes ago, genericeventhandler said:

Slightly cheating  but. 

@PART[InflatableHeatShield]
{
	@MODULE[ModuleAnimateGeneric]
	{
		@disableAfterPlaying = false
	}
}

Add this as a .cfg anywhere in the gamedata folder, and deflate the shield before dumping it,   

GE

I suddenly have a desire to do this at the same time I fire a KAS harpoon at the shield.  Pop!  Sounds like Kerbal engineering at its finest.

[gilflo]

I see you got 2 or 3 main engines at the center of your ship

Add  2 or 3 separators below your engines, then join them with a kind of empty tank, add a new separator for this tank with sepatrons, tweakscale them to be bigger, and set one inflatable shield below. You don't need 2 shields, just one bigger enough, 5m diameter or more if necessary..

When your chutes will be fully opened, you should be at your landing vertical speed between 500m and 1000m.

drop your shield and drop your empty tank then.....it will free all your engines....then open your gear

[Aegolius13]

At last... success (mostly)!   The single-shield design worked great, and kept the ship straight and cool on descent.  After my chutes deployed, I was down to about 7.5m/s.  And the heat shield, weighted down by my extra reaction wheels and a decoupler, fell non-explosively to the surface.

Only one more problem.  The heat shield fell... straight down.  And did not blow up on impact.  So when my lander also fell straight down, it landed right on top of the accursed heat shield.  That thing just will not leave me in peace.  

I guess I could try to use my main engines to angle away while I'm coasting down.   Or attach a couple sideways separatrons to the heat shield to blow it in one direction or another.  But these seem like manageable issues.  

Thanks again for y'all's help!

 

[Magzimum]

9 hours ago, Aegolius13 said:

The heat shield fell... straight down.  And did not blow up on impact.  So when my lander also fell straight down, it landed right on top of the accursed heat shield.  That thing just will not leave me in peace. 

I would just try a 2nd time, with the same craft.

Perhaps wiggly your ship a little with the WASD keys while hanging on the parachutes, so that the ship (and the heat shield) is not 100% horizontal when detaching, but a few degrees off the horizontal. I noticed that sometimes it will then flip itself, and accelerate quite a bit while it does that. You only need to get it to go faster than 9 m/s after all, and it should blow itself up. 

In fact, it may already reach speeds of over 9 m/s, so if the heat shield touches the ground first, it should blow up normally. The fact that it didn't may have been a fluke. Frankly, I think you nailed it, but you may have cursed the Kraken a few times too many. Just try again.

Hopefully you have a quicksave when you've got your parachutes deployed, so you can just try that part of the flight a few times, without all the tedious steps before it.

Edited September 21, 2016 by Magzimum

[Aegolius13]

13 hours ago, Magzimum said:

Hopefully you have a quicksave when you've got your parachutes deployed, so you can just try that part of the flight a few times, without all the tedious steps before it.

Funny you should mention that.  I have some saves with chutes fully deployed, but it turns out that as soon as the physics kick in, an uber-Kraken instantly annihilates my entire ship and even sends the camera back to space.  Luckily, I also had a save from just before chute deployment, I've done quite a bit more testing with that save, and, for posterity, here are the results:

• Trying to shimmy with my reaction wheels did not do much - my ship is pretty much locked in place.  This might be because my parachutes are spread pretty broadly over the top half of my craft.  I assume if they're closer to the CoM, it's easier to pivot.  
• Releasing the shield just after my chutes deployed (1000 meters above ground) seemed to give the heat shield enough of a drop to blow up on impact.  A couple of the other pieces of the drop rig survived, but my ship crushed them on landing without damage.  This might work even better if the chutes were set to deploy earlier.  
• I tried jettisoning the heat shield just as the chutes were slowing my ship down.  (i.e., at 10-20 m/s).  This worked: the shield dropped off safely, but started tumbling as it fell, moving it out of the landing zone.  I think the bit of remaining horizontal velocity did the trick here.
• I also tried giving the shield a little push by lighting up one of my off-center engines at the same time I jettisoned.  This worked very well: the shield tipped and started tumbling immediately.  This is probably similar to what a Separatron would do, but simpler and only costs a tiny bit of fuel.
• One semi-cheaty option.  First, dropping the heat shield at about 100 m/s velocity caused it to blow up, but (sometimes) did not destroy anything else on my ship.  
• And one very cheaty option: if I dropped the shield as soon as I reloaded (i.e., before physics kicked in), the shield flew upward right through my ship.  It might eventually fall down and hit me, though.  

So basically I guess I had some bad luck last night, when I could not get the shield to either budge or blow up in multiple attempts.  I think I'm going to call this ship the Hex, since it (1) uses a lot of six-way symmetry, and (2) is CURSED.

At any rate, I have now 100% successfully landed on Eve, and gotten back to orbit!  Now it's time to do it for real in career mode.  Thanks again for everyone's help!

[Magzimum]

5 hours ago, Aegolius13 said:

At any rate, I have now 100% successfully landed on Eve, and gotten back to orbit!  Now it's time to do it for real in career mode.  Thanks again for everyone's help!

Woohoo! *applauds*

Make sure to take some screenshots and post it in the mission reports!

[Aegolius13]

20 hours ago, Magzimum said:

Woohoo! *applauds*

Make sure to take some screenshots and post it in the mission reports!

Mission report posted at: